If you can share a schematic, I can give you the components to change.
If not, all "regular" clarifiers work basically the same. The external single Clarifier knob (not a split Coarse/fine) has RX only voltage going to it. Trace the middle (wiper) connection output and at some point, it will go through a diode. After the diode, you should see another diode connecting to the same circuit. That diode is from the TX only voltage circuit and it should come from a variable resistor.
To "unlock" the clarifier, you need to disconnect the diode on the TX only circuit and replace the RX only voltage on the external Clarifier with the same constant voltage.
Many external clarifier's, on the low side, go to ground through a resistor. For example, the 148GTL goes through a 3.3K to ground. Replace the fixed resistor with a variable that is ~2x larger - in that case a 5K (10 turn precision is best).
After making the changes, finish up by setting the clarifier to the 12:00 o'clock position and adjust the variable resistor going to ground to "align" the frequency.
This way you don't have to adjust any of the coils or anything else - you can zero beat it on TX or RX. Jut make sure your constant voltage source doesn't change by more than .02v between RX and TX.